The rewinding machine according to the invention is of the so-called peripheral winding type, that is, in which the roll is wound around a tubular core that is set in rotation between a group of three rollers that act on the periphery of the roll being formed and whose speeds are kept constant during the winding cycle.
The group of three motorized rollers forms a space of variable size so that the three roller are always in contact with the roll being made up, as said roll gradually increases in diameter. Two of the three rollers are placed at a set distance so as to define a throat through which the core is inserted and in which the sheet travels, whilst the third roller or pressure roller is mobile to allow the roll to increase in diameter and be discharged at the end of winding.
Of importance in these rewinding machines is the so-called changeover stage, that is, insertion of a new core in the winding space, accompanied by a special inserter, and unloading of the completed log, following breaking of the web of material.
This is achieved in a variety of ways according to the prior art, generally requiring sudden changes in the speed of two of the three winding rollers.
According to some known methods, the change in speed of these rollers causes tensioning and tearing of the web of paper following pinching thereof against the roller on which it is wound, pinching that can occur by means of the new core that is being inserted into the winding cradle. After breakage of the paper web, entry of the new core into the winding space and discharge of the made-up log take place through the difference in speed between the two input rollers and the two output rollers, respectively.
The system with tearing of the paper requires strong accelerations of the pressure roller, which cause stress on the machine structure, and does not guarantee precise cutting of the paper web.